The present invention relates to an improved lining hose for use in methods of rehabilitating a pipe conduit which is in a damaged or deteriorated state. More particularly, the present invention relates to an improved lining hose for use in softlining pipe rehabilitation methods wherein the lining hose is saturated with curable resin, introduced into a pipe conduit and shaped to conformingly line the pipe conduit where it is cured in place so as to form a rigid liner.
Various methods of rehabilitating a pipe conduit which is buried underground are known in the art. Generally speaking, such methods include the use of a liner having a diameter which is substantially the same as the inner diameter of the pipe conduit to be rehabilitated. The liner frequently includes an impermeable layer and an adjacent resin-absorbing layer. This resin-absorbing layer is impregnated with a liquid resin prior to the introduction of the thus treated liner into the pipe conduit. After being properly positioned in the pipe conduit, the liner is pressed against the inner surface of the pipe conduit by fluid pressure.
One such method of lining a pipe is disclosed in U.S. Pat. No. 4,009,063 which discloses a liner comprising a non-woven felt sandwiched between an outer membrane and an inner membrane of plastic sheet material. The non-woven felt material is impregnated with an uncured thermosetting resin. The resin is cured while the liner is held against the inner surface of the pipe conduit so as to form a rigid self-supporting liner. The alleged purpose of this impermeable outer layer is to avoid the need for cleaning the pipe conduit prior to installation of the liner.
Another method of lining a conduit is disclosed in U.S. Pat. No. 4,064,211. This method utilizes a liner having a resin impregnated inner layer and an impermeable layer outwardly bonded to and surrounding the inner layer. This liner is introduced into the interior of the pipe conduit by turning over one end region of the liner and causing the turned over region to gradually advance into the interior of the pipe conduit using an inversion process. During this inversion process, the resin impregnated layer is gradually transferred to the exterior of the lining hose by fluid pressure. The resin impregnated layer will contact the inner surface of the pipe conduit. In order to eliminate friction, the liner, before being turned inside out, is supported buoyantly by liquid which serves to carry the liner.
U.S. Pat. No. 4,770,562 discloses a method for rehabilitating a conduit using a lining hose having an outer impermeable layer surrounding and adjacent to an inner resin-absorbent layer. The resin-absorbent layer is saturated with an excess volume of resin. The outer impermeable layer is then perforated to form a plurality of flowthrough openings for the resin. The lining hose is subsequently introduced in a collapsed state into the pipe conduit, and the lining hose is shaped to conformingly line the pipe conduit. The shaping of the lining hose is accomplished by everting an auxiliary hose, also known as a calibration hose, inside the lining hose. The eversion of the calibration hose inside the lining hose will force the excess amount of resin through the flowthrough openings and into contact with the inner surface of the pipe conduit. The excess resin will also fill existing cracks and fissures in the conduit. A variation of the liner described in the U.S. Pat. No. 4,770,562 includes a relatively thin layer of resin-absorbent material outwardly adjacent to the impermeable surface. This thin layer of resin-absorbent material facilitates the spreading of the excess resin once the impermeable layer has been perforated and the shaping of the lining hose process has begun.
As previously stated, most liners in softlining applications utilize a layer of nonwoven felt for the resin absorbing layer of the lining hose. One of the purposes of the felt is to provide support for the uncured resin of the impregnated lining hose. The felt serves as a reservoir and/or carrier means for the uncured resin. Once cured, the resin provides the structural strength of the liner. The layer of felt is actually a deterrent to the strength of the liner after the resin has cured since it occupies space that could otherwise be filled with resin.
In the past, practitioners in the softlining industry have also utilized a layer of fiberglass for the resin absorbent member of the lining hose. U.S. Pat. 4,770,562 teaches such a use. A fiberglass mat provides greater structural strength for both the uncured and cured liner than does a mat of nonwoven felt. Despite its superior strength characteristics, fiberglass has not replaced felt as the preferred medium for the resin absorbing layer due to the wicking problems associated with fiberglass.
Fiberglass fibers have a high resistance to stretching. The resin in a cured-in-place liner bonds or adheres to fiberglass fibers upon curing. Due to the bond between the resin and the fiberglass fibers, the resin also becomes more resistant to stretching when axial or radial loads are applied to the cured liner. Thus, the cured resin is reinforced by fiberglass so long as the bond between the resin and fiberglass is not broken.
Cured-in-place liners are typically installed in environments that are continuously exposed to water and other corrosive materials. Cured-in-place liners are also exposed to varying temperatures and flow conditions. The bond between the fiberglass and cured resin is subject to constant stress and strain due to the different coefficients of expansion of resin and fiberglass. Over time, the repeated expansion and contraction of the resin and fiberglass, caused by the varying temperature and flow conditions, will create tiny spaces between the resin and the fiberglass fibers.
With conventional cured-in-place liners using fiberglass, the fiberglass fibers located on the inner and outer surfaces of the liner are exposed to the water and other corrosive materials. Due to capillary or wicking action, the water and other corrosive materials are absorbed into the tiny spaces adjacent to the exposed fiberglass fibers. The absorption of water and other corrosive materials enhances the expansion and contraction of the resin and fiberglass, thereby further deteriorating the bond between the resin and fiberglass. Corrosive reactions with the resin/fiberglass laminant also exacerbates the deterioration of the bond between the resin and fiberglass. As a result of the wicking action, the space between the resin and fiberglass fibers becomes progressively larger and larger. In addition, as the space between the resin and a given fiber grows in size and length, previously unexposed fiberglass fibers adjacent to the exposed fibers become exposed to the water and other corrosive materials. Over time, the wicking of water and other corrosive materials into the laminant will destroy the bond between the resin and the fiberglass fibers. When this occurs, the reinforcing effects of the fiberglass is lost causing the liner to lose much of its structural strength, thereby ending the useful life of the liner prematurely.
Other reinforcing materials, such as Kevlar.TM. and carbon fibers, may be used as substitutes for nonwoven felt. However, these materials may also experience the problems associated with fiberglass when exposed to water and other corrosive materials.
The present invention overcomes the wicking problems associated with the use of fiberglass and other reinforcing fibers. The lining hose of a preferred embodiment of the present invention sandwiches a layer of fiberglass, or other desirable reinforcing fiber, between an inner and outer layer of resin absorbent material. The resin absorbent material, such as nonwoven felt, is saturated with curable resin. Upon curing, the resin in the inner and outer resin absorbent layers encapsulate the fiberglass layer and protects it from water and other corrosive materials. Thus, the resin absorbent material acts as a protective veil surrounding the layer of reinforcing fiber. Wicking problems are virtually eliminated because the reinforcing fibers are not exposed to water or other corrosive materials.